A conventional flywheel type rotor of a magnetic generator is illustrated in FIG. 8, FIG. 9 and FIG. 10. A rotor of a magnetic generator is generally connected to a rotary shaft such as a crankshaft or the like of an engine (not shown in the figures). A magnetic generator, an ignition coil, capacitor and the like elements are disposed on an inside space of the rotor, and electric power from the magnetic generator is used to provide ignition for the engine.
In FIGS. 8-10, a rotor 10 comprises a flywheel 1, a boss 2, a plurality of permanent magnets 3, and a magnet-holding cylinder 5. The flywheel 1 is bowl-shaped and has a peripheral wall part 1a and a disc part 1b. The boss 2 is fixed on the center of the disc part 1b of flywheel 1 and is connected to a rotary shaft of an engine. The permanent magnets 3 are circularly disposed on an inner surface of the peripheral wall 1a of flywheel 1. Plural protrusion parts (or offset parts) 4 for positioning the permanent magnets 3 in an axial direction of the rotor 10 are formed on the peripheral wall 1a of the flywheel 1 by partially extruding the peripheral wall 1a at positions close to where the permanent magnets 3 are to be disposed.
Magnet holding cylinder 5 has an outward flange 5a, as best seen in FIG. 11, formed of an iron plate or a stainless steel sheet. An outer surface of a cylindrical part 5b of the magnetholding cylinder 5 contacts inner surfaces 3a of the permanent magnets 3 so as to prevent them from moving in the radial direction of the rotor 10. Outward flange part 5a contacts surfaces 3b of the permanent magnets 3 facing to the open end 1c of the flywheel 1 for positioning or fixing the permanent magnets 3 in the axial direction of the rotor 10, to prevent their motion in the axial direction.
Spaces formed between the permanent magnets 3, the flywheel 1 and the magnet-holding cylinder 5 are filled by resin molded member 6 for integrating them into one piece. Protrusions 7 for preventing disconnection of the resin molded member 6 are formed on the peripheral wall 1a of the flywheel 1 by partially pressing thereof at positions between each of the permanent magnets 3.
As mentioned above, the permanent magnets 3, which are to be disposed on the peripheral wall 1a of the flywheel 1, are positioned in the axial direction of the rotor 10 by contacting with the plural protrusion parts 4 in the conventional rotor of the magnetic generator. The protrusion parts 4, however, needs large scale arrangements for being pressed. As a result manufacture of such a rotor 10 has the disadvantages of high cost and low productivity.